1. Field of the Invention
The present invention relates to a video game device wherein a three-dimensional (hereinafter simply ‘3D’) model constituted by a plurality of polygons having vertices associated with clusters for defining an object to be deformed is deformed in conformity with a drawing period from data of each of frames relating to a motion sequence, a 3D model deformation program employed in this video game device, a recording medium which stores the 3D model deformation program and a 3D model deformation method.
2. Description of the Related Art
Conventionally, the characters appearing in video games, such as for example characters modeled on human beings, are constituted by models comprising the various parts of the human body, such as head, upper arm, lower arm, hand, breast, waist, thighs, shins and feet, such models being formed by putting flesh on bones (skeleton) employed solely for the purpose of position setting. Specifically, these models are usually constituted by a plurality of polygons, the vertices of these polygons being regulated and managed as positional data from the central co-ordinates of the bones (i.e. reference co-ordinates constituting co-ordinates taken as reference for setting the bone positions). When a motion sequence of a character is to be displayed in a video game, the shape of the character in a frame at a given instant is found by calculating the positions of the bones in this frame and then calculating the positions of the vertices of the polygons which are attached to these bones.
However, when a character is represented using a skeleton as described above, the skeleton is set for each part of the human body and fine deformation processing of the character cannot be performed. For example, if a single model (skeleton) is set up for the head of a character, although overall operations such as inclining the head can be represented, detailed facial expressions of the character cannot be represented.
On the other hand, in the field of computer graphics, cluster deformation processing is performed in which clusters are associated with a plurality of vertices of the polygons constituting a three-dimensional (hereinafter simply ‘3D’) model and the plurality of vertices associated with these clusters are moved by moving the cluster in question.
For example, facial animation tools such as the FAMOUSfaces animator (manufactured by Famous Technologies, Pty. Ltd.) are employed in the field of computer graphics. With this software, movement of vertices is achieved by setting up clusters in respect of groups obtained by grouping a plurality of vertices of a polygon or NURBS model constituting a 3D model, so that the vertices belonging to each cluster in question can be moved. Also, a single vertex can be associated with a plurality of clusters and weightings set up indicating the degree of association of the vertex in question with respect to each cluster; the vertex in question can then be moved in accordance with the weightings of the plurality of clusters.
In this way, in deformation processing of a 3D model using the above clusters, fine deformation of the 3D model can be achieved and complex human facial expressions etc can easily be created; however, when deformation processing of a 3D model is applied to a video game, it is necessary to draw the game image including that of the character appearing in the video game rapidly with every frame period.
However, in order to perform such drawing, an enormous amount of positional calculation in respect of the vertices of a large number of polygons must be performed so this calculation cannot be processed within the frame period; thus 3D model deformation processing using clusters as employed in the field of computer graphics cannot be directly applied to video games.